Disclosure of Invention
The invention overcomes the defects in the prior art, provides the dendritic PtPdCu nano particles for electrocatalytic oxygen reduction and the preparation method thereof, researches a simple and easily-repeated preparation method, prepares the dendritic PtPdCu nano particles, and not only can reduce the utilization rate of platinum but also can reduce the binding energy between the platinum and a hydrogen-oxygen bond by changing the electronic structure of the platinum so as to improve the catalytic performance of the oxygen reduction reaction.
The purpose of the invention is realized by the following technical scheme.
The dendritic PtPdCu nano particle for electrocatalytic oxygen reduction and the preparation method thereof are carried out according to the following steps:
step 1, mixing palladium salt and hydrochloric acid according to a molar ratio of (1-4): 4, uniformly mixing to obtain a palladium precursor solution, wherein the molar concentration of the palladium precursor solution is (5-20) mM;
step 2, placing 0.160g-0.450 weight part of tannic acid into a reaction container, and sequentially dripping 0.5-2.5mL of the palladium precursor solution prepared in the step 1, 0.5-16mL of copper chloride solution and 0.5-5mL of chloroplatinic acid solution into the reaction container at a dripping rate of 5-10 drops/min, and adding deionized water into the solution to obtain a mixed solution, wherein the total volume of the mixed solution is 25-35 mL;
step 3, uniformly stirring the mixed solution prepared in the step 2 at the room temperature of 20-25 ℃, transferring the mixed solution into a reaction kettle, preserving the heat at the temperature of 80-120 ℃ for 4-8h, cooling the mixed solution to the room temperature of 20-25 ℃ in a furnace cooling mode, and then cooling the mixed solution at the cooling rate of 1-5 ℃/min to obtain a black mixed solution;
and 4, centrifuging the black mixed solution prepared in the step 3, and washing the black mixed solution by using a mixture of deionized water and ethanol to obtain the dendritic PtPdCu nano particles for electrocatalytic methanol oxidation.
In step 1, the molar ratio of palladium salt to hydrochloric acid is 1: and 2, adopting 99 mass percent (59 percent of Pd%) palladium chloride powder as the palladium salt, wherein the molar concentration of the palladium precursor solution is 10 mM.
In the step 2, the dosage of the tannic acid is 0.175-0.400 part by weight, the dosage of the palladium precursor solution is 0.5-2mL, the concentration of the copper chloride solution is 5mM, the dosage of the chloroplatinic acid solution is 1-15mL, the dosage of the chloroplatinic acid solution is 1-4mL, the dosage of the chloroplatinic acid solution is 5mM, and the total volume of the mixed solution is 28-32 mL.
In step 3, stirring for 12-18min, keeping the temperature at 90-110 ℃ for 5-7h, cooling to room temperature of 20-25 ℃ in a furnace, and cooling at the rate of 2-3 ℃/min.
In step 4, the conditions of centrifugation are: the rotation speed is 15000-20000rpm, and the centrifugation time is 8-12 min.
The phase and morphology of the PtPdCu nano particles are characterized by X-ray diffraction (XRD) and a Transmission Electron Microscope (TEM), so that the dendritic PtPdCu nano particles with different components are successfully prepared, and the average size is 22-26 nm. Pt prepared by the method of example 1 was obtained from Linear voltammetry (LSV)37Pd20Cu43Nanoparticles in acidic conditions (0.1M HClO)4) Polarization curves at different rotation speeds indicate that the Pt37Pd20Cu43The nano-particles have excellent performance of electrochemically catalyzing oxygen reduction, and the oxygen reduction catalysis performance of the nano-particles prepared by the method under the acidic condition is that the average limiting current density is 0.95-1.05mA cm-2The initial potential is 920-950mV on average. From FIG. 1, it can be seen that Pt prepared by the method of example 137Pd20Cu43The nanoparticles have a face-centered cubic structure, and as can be seen from fig. 2, the morphology thereof is a dendritic core-shell structure with palladium copper as a core and platinum as a shell. As can be seen from FIG. 3, the PtPdCu nanoparticles prepared by the method are prepared under acidic conditions (0.1M HClO)4) The oxygen reduction catalytic performance of 1600r is that the limiting current density reaches 0.98mA cm-2The initial potential was 938 mV. From FIG. 4, it can be seen that Pt prepared by the method of example 232Pd16Cu52The shape of the nano-particles is a dendritic structure, and the nano-particles are slightly porous. FIG. 5 shows the Pt method in example 334Pd31Cu35The dendritic morphology of the nanoparticles is not obvious, but the size is reduced. As can be seen from FIG. 6, Pt prepared by the method of example 433Pd12Cu55The nanoparticles are agglomerated but are still small-sized, irregular core-shell structures.
The invention has the beneficial effects that: the PtPdCu nano catalyst with different components and excellent performance on electrocatalytic oxidation reduction is prepared by a one-step synthesis method which has the advantages of simple process, easy operation, easy control of the shape, the size and the good repeatability of a product; the invention also realizes the change of the product components by regulating and controlling the process parameters, which provides reference for simplifying the preparation process and controllably preparing the components of other noble metal nano-particles and has certain guiding significance.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples.
Example 1
1) Mixing palladium salt (palladium chloride powder with the mass fraction of 99 percent (Pd percent is 59 percent)) and hydrochloric acid (hydrogen chloride) according to the molar ratio of 1:2 to obtain a palladium precursor solution;
2) weighing 0.175g of tannic acid, sequentially dropping 1mL of 10mM palladium precursor solution, 1mL of 5mM copper chloride solution and 2mL of 5mM chloroplatinic acid solution at the dropping rate of 8 drops/min, and adding 26mL of deionized water to make the total volume of 30 mL;
3) continuously stirring the mixed solution obtained in the step 2) at room temperature for 15min, transferring the mixed solution into a stainless steel high-pressure reaction kettle, heating the mixed solution at 100 ℃ for 6h, cooling the mixed solution to room temperature in a furnace at a cooling rate of 3 ℃/min to obtain a black mixed solution;
4) centrifuging the mixed solution obtained in the step 3) for 10min at 18000rpm by a centrifuge, and washing the mixed solution by using a mixture of deionized water and ethanol to finally obtain dendritic Pt37Pd20Cu43And (3) nanoparticles.
The phase and morphology of the Pt are characterized by X-ray diffraction (XRD) and Transmission Electron Microscope (TEM), and the dendritic Pt is prepared in the embodiment37Pd20Cu43And (3) nanoparticles. The nanoparticles were obtained from linear voltammetry (LSV) under acidic conditions (0.1M HClO)4) Shows the polarization curve of the Pt37Pd20Cu43The nanoparticles have excellent performance in electrochemically catalyzing oxygen reduction.
FIG. 1 is an example1 method of preparing Pt37Pd20Cu43The X-ray diffraction pattern of the nanoparticles shows that the PtPdCu nanoparticles prepared by the method are of a face-centered cubic structure as shown in FIG. 1, and show that the PtPdCu nanoparticles are of a dendritic core-shell structure with palladium copper as a core and platinum as a shell as shown in FIG. 2. As can be seen from FIG. 3, the nanoparticles prepared by the present method were under acidic conditions (0.1M HClO)4) The oxygen reduction catalytic performance of the catalyst is that the limiting current density reaches 0.98mA cm-2The initial potential was 938 mV.
Example 2
1) Mixing palladium salt (palladium chloride powder with the mass fraction of 99 percent (Pd percent is 59 percent)) and hydrochloric acid according to the molar ratio of 1:2 to obtain a palladium precursor solution;
2) weighing 0.3g of tannic acid, sequentially dropping 1mL of 10mM palladium precursor solution, 6mL of 5mM copper chloride solution and 2mL of 5mM chloroplatinic acid solution at a dropping rate of 5 drops/min, and adding 21mL of deionized water to make the total volume of 30 mL;
3) continuously stirring the mixed solution obtained in the step 2) at room temperature for 12min, transferring the mixed solution into a stainless steel high-pressure reaction kettle, heating the mixed solution at 120 ℃ for 4h, cooling the mixed solution to room temperature in a furnace, and obtaining a black mixed solution, wherein the cooling rate is 5 ℃/min;
4) centrifuging the mixed solution obtained in the step 3) for 12min at 15000rpm by a centrifuge, and washing the mixed solution by a mixture of deionized water and ethanol to finally obtain dendritic Pt32Pd16Cu52And (3) nanoparticles.
FIG. 4 shows Pt prepared by the method of example 232Pd16Cu52As shown in FIG. 4, the PtPdCu nanoparticles prepared by the method have a dendritic structure and a few pores.
Example 3
1) Mixing palladium salt (palladium chloride powder with the mass fraction of 99 percent (Pd percent is 59 percent)) and hydrochloric acid according to the molar ratio of 1:2 to obtain a palladium precursor solution;
2) weighing 0.4g of tannic acid, sequentially dripping 1mL of 10mM palladium precursor solution, 10mL of 5mM copper chloride solution and 2mL of 5mM chloroplatinic acid solution at the dripping rate of 10 drops/min, and adding 17mL of deionized water to make the total volume of 30 mL;
3) continuously stirring the mixed solution obtained in the step 2) at room temperature for 18min, transferring the mixed solution into a stainless steel high-pressure reaction kettle, heating the mixed solution at 80 ℃ for 8h, cooling the mixed solution to room temperature in a furnace at a cooling rate of 1 ℃/min to obtain a black mixed solution;
4) centrifuging the mixed solution obtained in the step 3) by a centrifuge at 20000rpm for 8min, and washing with a mixture of deionized water and ethanol to obtain dendritic Pt34Pd31Cu35And (3) nanoparticles.
FIG. 5 shows Pt prepared by the method of example 334Pd31Cu35In the transmission electron microscope image of the nanoparticles, as shown in fig. 5, the PtPdCu nanoparticles obtained by the method of example 3 have a less pronounced dendritic morphology but a reduced size.
Example 4
1) Mixing palladium salt (palladium chloride powder with the mass fraction of 99 percent (Pd percent is 59 percent)) and hydrochloric acid according to the molar ratio of 1:2 to obtain a palladium precursor solution;
2) weighing 0.4g of tannic acid, sequentially dropping 1mL of 10mM palladium precursor solution, 15mL of 5mM copper chloride solution and 2mL of 5mM chloroplatinic acid solution at the dropping rate of 9 drops/min, and adding 12mL of deionized water to make the total volume of 30 mL;
3) continuously stirring the mixed solution obtained in the step 2) at room temperature for 16min, transferring the mixed solution into a stainless steel high-pressure reaction kettle, heating the mixed solution at 110 ℃ for 5h, cooling the mixed solution to room temperature in a furnace at a cooling rate of 3 ℃/min to obtain a black mixed solution;
4) centrifuging the mixed solution obtained in the step 3) for 9min at 17000rpm by a centrifuge, and washing the mixed solution by using a mixture of deionized water and ethanol to finally obtain dendritic Pt33Pd12Cu55And (3) nanoparticles.
FIG. 6 shows Pt prepared by the method of example 433Pd12Cu55As can be seen from FIG. 6, the PtPdCu nanoparticles prepared by the method are agglomerated, but still have a small-sized core-shell structure.
Example 5
1) Mixing palladium salt (palladium chloride powder with the mass fraction of 99 percent (Pd percent is 59 percent)) and hydrochloric acid according to the molar ratio of 1:1 to obtain a palladium precursor solution;
2) weighing 0.45g of tannic acid, sequentially dropping 0.5mL of 20mM palladium precursor solution, 16mL of 5mM copper chloride solution and 5mL of 5mM chloroplatinic acid solution at the dropping rate of 8 drops/min, and adding 13.5mL of deionized water to make the total volume 35 mL;
3) continuously stirring the mixed solution obtained in the step 2) at room temperature for 16min, transferring the mixed solution into a stainless steel high-pressure reaction kettle, heating the mixed solution at 110 ℃ for 7h, cooling the mixed solution to room temperature in a furnace at a cooling rate of 3 ℃/min to obtain a black mixed solution;
4) centrifuging the mixed solution obtained in the step 3) for 9min at 18000rpm by a centrifuge, and washing the mixed solution by using a mixture of deionized water and ethanol to finally obtain the dendritic PtPdCu nanoparticles.
Example 6
1) Mixing palladium salt (palladium chloride powder with the mass fraction of 99 percent (Pd percent is 59 percent)) and hydrochloric acid according to the molar ratio of 1:4 to obtain a palladium precursor solution;
2) weighing 0.16g of tannic acid, sequentially dropping 2.5mL of 0.5mM palladium precursor solution, 0.5mL of 5mM copper chloride solution and 0.5mL of 5mM chloroplatinic acid aqueous solution at the dropping rate of 7 drops/min, and adding 21.5mL of deionized water to make the total volume of the tannic acid to be 25 mL;
3) continuously stirring the mixed solution obtained in the step 2) at room temperature for 18min, transferring the mixed solution into a stainless steel high-pressure reaction kettle, heating the mixed solution at 100 ℃ for 7h, cooling the mixed solution to room temperature in a furnace, and obtaining a black mixed solution, wherein the cooling rate is 4 ℃/min;
4) centrifuging the mixed solution obtained in the step 3) by a centrifuge at 16000rpm for 11min, and washing by using a mixture of deionized water and ethanol to finally obtain the dendritic PtPdCu nanoparticles.
The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.